Though R2-D2 may be the most famous droid in all of Star Wars, he obviously wasn't the first to roll off the assembly line. Heck, he wasn't even in the first series: after all, you can't have an R2 until after you have an R1.
An old model astromech droid abandoned after the capture of its owner, R1-G4 was one of the droids that the Jawas scavenged to rebuild and sell to Tatooine colonists. Using cobbled-together weaponry, the Jawas probably incapacitated the droid then dragged it to their immense treaded sandcrawler. R1-G4 was one of the droids rounded up when Imperial stormtroopers arrived on Tatooine looking for the escaped droids R2-D2 and C-3PO.
If you ask the Expanded Universe nerds, they'll tell you the entire R-series of astromech droids was created by the Industrial Automaton company, and that specific flaws with the R1s led directly to improvements seen in the R2s. If you ask anyone else, they might vaguely remember the giant green robot that stood in one place
and looked like a water heater. Maybe. It was basically scenery, and there were much more interesting things happening in front of it at the time.
Considering this is a droid that only had about five seconds' worth of screentime in Star Wars, Hasbro really went all-out on our boy R1-G4, here. It's not just that they did a good job of duplicating all the various body details - which they did - but that there seem to be different textures on the pieces. There are scratches, dents and rivets all over the place, evidence of the rough life this droid has led. It's the type of thing you really have to get up-close and examine the figure to see, but it's damn cool.
As a non-humanoid droid, R1 doesn't have to worry about the normal sorts of articulation. His "head" spins around, but that's really it. It's tough to get moving at first, but turns smoothly: none of that annoying clicking seen in other droids. The biggest surprise is that his little grasping arms can extend a bit. It's just a small distance - say, ¼" - but it adds a bit of fun to the figure.
The paint is fantastic.
The bulk of the figure is a bluish green, and there are yellow stripes highlighting some of the edges. The panels in the mid-body have clean white apps on the surface, and the vent on its back is silver. There are white and pale yellow graphics around the head. The lower body has some silver speckles, and the bigger dents are done the same. Even the bottom of the figure is fully sculpted and painted - R1 units get around via a single tread, which couldn't have been very useful on a desert planet like Tatooine.
Counting the antenna on the top of this droid's head, R1-G4 stands nearly 5" tall - yes, it's taller than most of the actual characters. Of coure, since it was basically scenery, that isn't such a bad thing. Back when this monster was first announced, Hasbro was trying to figure out a way to include a Jawa with it, so people would have a better idea of just what scene it was from. Obviously that didn't work out, but it's no great loss. The sculpt and paint on R1-G4 are high quality, even by modern standards, so the only downside is if you're building a "purchase of the droids" diorama, R1-G4 might outshine all the other figures in the scene.